Quark and Gluon Angular Momentum in the Nucleon
Matthias Burkardt, Hikmat BC, and Abdullah Jarrah (New Mexico State, University)
TL;DR
This paper explores the distribution of quark and gluon angular momentum in the nucleon, deriving the Ji relation from impact parameter space distributions and comparing different spin decompositions using various models.
Contribution
It provides an intuitive derivation of the Ji relation from impact parameter space distributions and compares spin decompositions in different theoretical models.
Findings
Impact parameter space distributions show significant axial symmetry deviation with polarization.
The Ji and Jaffe-Manohar decompositions are compared in scalar diquark and QED models.
Spectator effects are estimated using the MIT bag model, highlighting gluon vector potential influence.
Abstract
Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, are exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. From this deformation, we present an intuitive derivation of the Ji relation. In a scalar diquark model and in QED, we compare the Ji and Jaffe-Manohar decompositions of the nucleon spin. Using the MIT bag model, we estimate spectator effects through the presence of the gluon vector potential in the definitions of the quark orbital angular momentum.
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